Mining specialization is against the purpose of cryptocurrency mining because it gives specialized attackers (a centralized group) power over the rest of the stakeholders (not just owners, but users).
It is common to make analogous mistakes when considering biological evolution.
The opportunity for miners to collude is completely offset by the fact that if they try to leverage their equipment somehow to delay or otherwise impact the main chain, you can just choose to mine instead to make better profits. Thus far there hasn’t been a single effective counter-play for miners that isn’t just “mine more Bitcoins and thus further secure the network” that isn’t just day trading with extra steps.
Also who are these centralized miners anymore? Pools are centralized, but I’m a nobody who can mine profitably with very little capital involved. I can submit whatever block template I want. I haven’t been invited to any meetings.